PubMed · 2026-09-01
Algae, cyanobacteria, diatoms, and other water-dwelling photosynthesizers all rely on internal CO2-pumping systems to fix carbon efficiently, since none of them can get enough CO2 through their basic enzyme machinery alone. This research maps how different aquatic organisms evolved distinct solutions to the same problem: water makes it hard to get CO2 to the cellular engine that builds sugar from sunlight.
None of the surveyed aquatic species can achieve CO2-saturated photosynthesis through Rubisco kinetics alone; all depend on CO2-concentrating mechanisms (CCMs)
CCM effectiveness (Kcair/Km CO2 ratio) is consistently higher in organisms with Rubisco-containing microcompartments like pyrenoids and carboxysomes, though pyrenoids aren't strictly necessary for concentrating CO2 above ambient levels
An inverse relationship between Rubisco carboxylation efficiency and CO2 affinity reveals aquatic organisms followed a different CCM-Rubisco coevolutionary path than terrestrial plants, likely shaped by oxygen buildup in submerged conditions
